The realization of FIR filter by frequency sampling realization can be viewed as cascade of two filters.

Explanation:
Frequency sampling is a method used to design finite impulse response (FIR) filters. In this method, the desired frequency response of the filter is sampled at equally spaced frequencies and then an inverse Fourier transform is performed to obtain the filter coefficients.

When a FIR filter is realized using frequency sampling, it can be viewed as a cascade of two filters: the analysis filter and the synthesis filter.

1. Analysis Filter:
The analysis filter is the first stage in the frequency sampling realization. It is designed to have the desired frequency response of the filter. The analysis filter samples the input signal at equally spaced frequencies and computes the Fourier coefficients of the signal.

2. Synthesis Filter:
The synthesis filter is the second stage in the frequency sampling realization. It is designed to reconstruct the original signal using the Fourier coefficients obtained from the analysis filter. The synthesis filter takes the Fourier coefficients as input and performs an inverse Fourier transform to obtain the filter coefficients.

Cascade of Two Filters:
The output of the analysis filter is the input to the synthesis filter. Therefore, the frequency sampling realization can be viewed as a cascade of these two filters. The analysis filter samples and computes the Fourier coefficients of the input signal, and the synthesis filter reconstructs the original signal using these coefficients.

The cascade of two filters allows the frequency sampling realization to accurately capture the desired frequency response of the FIR filter. Each filter stage performs a specific function in the realization process, and together they provide an effective and efficient method for designing FIR filters.

In conclusion, the realization of FIR filter by frequency sampling can be viewed as a cascade of two filters: the analysis filter and the synthesis filter.